Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 221142

Area Forecast Discussion
National Weather Service Quad Cities IA IL
542 AM CST Mon Jan 22 2018


Issued at 340 AM CST Mon Jan 22 2018

At 3 am a strong upper level low was over central KS with an
associated surface low over far northwest MO. A warm front
extended east-northeast from this low across northern MO,
southeast IA into north central IL. Temperatures and dewpoints
were in the 50s south of the boundary, while temperatures ranged
from the mid 30s north to mid 40s south over areas of eastern IA
and northern IL north of the boundary. Area radars showed a swath
of warm advection showers and thunderstorms lifting north of the
highway 20 corridor, while a separate south to north band was
along the MS river south of BRL, streaming north to northeast into
northern IL. Dense fog that formed north of the warm front over
the forecast area continues to thin out from the rain, but a few
pockets of low visibilities remain, mainly north of I-80 and east
of the MS river.


.SHORT TERM...(Today and Tonight)
ISSUED AT 340 AM CST Mon Jan 22 2018

Numerous forecast challenges this morning as the surface and upper
level lows lift northeast through the forecast area today and
tonight. Initially, fog and thunderstorms will become less of an
issue early this morning, then focus will be on the potential for
additional afternoon thunderstorms along the warm front with the
passing upper level low later today. Colder air wrapping into the
area behind the system and deformation axis will likely provide a
period of snow overnight with light accumulations possible.

The dense fog will be confined mainly just north of the slowly
advancing warm front with stronger winds well to the north and
south of the boundry further limiting fog redevelopment. At the
current rate, may be able to cancel the remaining dense fog
advisory over northwest IL early.

Very mild air will result in highs reaching the mid to potentially
upper 50s over the south, but further north, just how far the
warm front advances will be critical to how warm it gets and for
now have highs around 40 along highway 20.

Current trends suggest a dry period for all but the north and
northeast this morning before the upper level dry slot lifts
through and possibly fires showers and thunderstorms over
especially areas east of the MS River. SPC has a marginal threat
for severe storms over northern IL including the I-80 corridor
east of the Quad Cities. The amount of warming, instability and
critical locations of surface boundaries and possible meso-lows
will be critical as to the potential for low top supercells in a
potential high shear/low cape severe weather environment roughly
from mid afternoon into early evening. Both synoptic models and
convective allowing models vary considerably with these features
and thus forecast confidence is low, but the situation will be
monitored closely during the day.

Tonight, the deformation zone with the passing system and in-
building cold air advection suggests rain changing to light snow
with accumulations of an inch or so over far northwest IL with
much lighter amounts elsewhere.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 340 AM CST Mon Jan 22 2018

A warming trend through the week before turning colder next weekend.

Lingering light snow or flurries will end Tuesday morning in the far
eastern areas. Otherwise expect windy, dry and much cooler
conditions across the area.

Quiet and dry conditions will continue Tuesday night through
Wednesday night as high pressure moves through the Midwest.
Temperatures should average slightly above normal.

Thursday on...

The quiet and dry conditions will continue Thursday and Thursday
night as warmer air moves into the area. Temperatures will average
above normal. Attention then turns to the next storm system.

All global models have a storm system affecting the eastern half of
the country late this week. However, differences in storm track
continue and unlike yesterday there are now differences with timing.

The ECMWF is a bit slower and further to the east with the storm
system while the GFS is faster and further to the west. The CMC
global is a bit slower than the GFS but further west.

Right now the model consensus has slight chance pops for rain Friday
afternoon. Taking the moist bias of the models into consideration,
the possibility does exist that the daylight hours of Friday might
be dry. Regardless, temperatures on Friday will be well above normal.

Friday night into Saturday the model consensus has chance pops for
rain with a rain/snow mix or possibly all snow late Friday night and
early Saturday morning.

Saturday night and Sunday the model consensus has much cooler and
dry conditions as another high pressure moves through the Midwest.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 542 AM CST Mon Jan 22 2018

A strong low pressure system will pass through the region today,
leading to changing weather conditions. IFR to LIFR conditions
early this morning due to fog and low clouds may improve for a
period to MVFR or even VFR as a warm front, already north of BRL
continues to advance northward during the day. This will cause
brisk east to northeast winds to veer to the south during the day
with scattered showers redeveloping in the afternoon and evening.
There is a low potential for thunderstorms at especially MLI and
BRL, which is not mentioned in the current forecasts. Tonight,
conditions will deteriorate again to IFR or lower with winds
veering to the northwest, causing rain to change to snow with
associated visibility restrictions.


IL...Dense Fog Advisory until 6 AM CST early this morning for Carroll-
     Jo Daviess-Stephenson-Whiteside.



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